Similarity matrix
On Tuesday 10 April 2001 22:55, Frank E Harrell Jr wrote:
I frequently use hclust on a similarity matrix. In R only a distance matrix is allowed. Is there a simple reliable transformation of a similarity matrix that will result in a distance matrix making hclust work the same as S-Plus with a similarity matrix? Venables & Ripley 3rd edition implies that a simple reversal of values will suffice. Thanks -Frank
Legendre & Legendre (Numerical Ecology, 2nd ed., Elsevier) give a choice of D=1-S, D= sqrt(1-S), or D=sqrt(1-S^2) (p. 252) and list the respective properties of the first two (Table 7.2, p. 275). Basically, the properties of the resulting distance coefficient will depend on the kind of similarity coefficient you used (of which the book offers an amazing variety). Cheers Kaspar Pflugshaupt
Kaspar Pflugshaupt Geobotanical Institute ETH Zurich, Switzerland -.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.- r-help mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html Send "info", "help", or "[un]subscribe" (in the "body", not the subject !) To: r-help-request at stat.math.ethz.ch _._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._